Car drawings

Collection of Car Drawings i have done, using Photoshop for some contrast, lightpad, pencil for outlines, then Spectrum Noir Illustrator markers, Copic Ciao&Sketch markers, Sakura Pigma Fineliners, white gel pen.
After i did the first two Supras for friends of mine of their own cars, neighbours and fellow car enthousiasts from friends and car clubs started asking they wanted the same thing of their cars. So i did, i charged a ridiculous low price for them seen the time it cost me (it wouldn't even cover half the hours i spent on each, especially not combined with the cost of some markers), but i had something to do and i used the funds to buy more markers and other art supplies.
I am on welfare, medical reasons, so this keeps my art going, and i am not too sure of myself how much i could or should ask.

They're all A4 size except for the Nissan GTR and Honda two cars, those are A3. I did charge more for those.